A wireless telecommunications system has been proposed with a central terminal, or station, arranged to communicate via wireless links with a plurality of subscriber terminals, or stations, at subscriber locations to implement a wireless telephony system. The system is intended to be used with fixed subscriber locations rather than the more familiar mobile cellular telephone systems.
The system finds a wide variety of possible applications, for example in rural, remote, or sparsely populated areas where the cost of laying permanent wire or optical networks would be too expensive, in heavily built-up areas where conventional wired systems are at full capacity or the cost of laying such systems would involve too much interruption to the existing infrastructure or be too expensive, and so on.
The central terminal is connected to a telephone network and exists to relay messages from subscribers in the cell controlled by the central station to the telephone network, and vice versa. In a typical arrangement, a central terminal may have a plurality of modems for supporting a plurality of subscriber links to subscriber terminals. Each subscriber terminal may be able to support more than one line, and so the number of lines supported may be greater than the number of links.
Typically, a plurality of modems at the central terminal may share one connection to the exchange through which all calls to and from subscriber terminals supported by those modems pass. These calls are sent over this single connection in blocks called frames, a frame consisting of a number of timeslots. The exchange will place a call for a particular subscriber terminal on a particular timeslot, so that call information destined for a particular subscriber terminal can be extracted by the central terminal and passed to the appropriate modem for sending over a wireless link to that subscriber terminal. Hence, the central terminal performs fixed timeslot mapping to map calls from particular timeslots in the exchange--central terminal connection to particular wireless links to subscriber terminals, and vice versa, thereby routing calls between the subscriber terminals and the exchange.
Thus, it will be apparent that the central terminal currently has little flexibility in the way it manages calls.